Once designed, distance education courses must be delivered to learners. Course delivery normally involves interaction between learners and instructors. Courses are delivered through symbol systems called media —

• text media,
• sound (audio) media,
• pictures (visual) media,
• realia (things) , or combinations of these.

Media are distributed through a variety of technologies, mainly print, computer, recorded audio or video tapes, discs or cassettes, radio or television broadcasting, audio, video, or computer teleconferencing, or in packages of materials. Combinations of media may be packaged for delivery via the Internet, including the World Wide Web.

Each medium is best suited to communicating a particular type of message. And different media are preferred by different learners. So a key challenge in designing a distance education course is media selection—finding the most cost-effective mix of media.